Ecosystems of the Marshall Islands

The Marshalls contain one of the richest natural ecosystems on earth - the coral reef. The coral reef has been said to be even richer than the rainforest, which is so famous for its remarkable number and variety of species. Furthermore, the coral reef is extolled as being more attractive than the rainforest because its beauty and vast array of colorful species are readily seen even by untrained observers.

The Marshall Islands' coral reef is home to well over 800 species of fishes. 1,600 species of mollusks, and more than 250 species each of algae and stony corals. Added to all this are numerous other invertebrates, and birds that fly overhead. Since the coral reef of the Marshalls is found on both the ocean and lagoon sides of the atolls, in terms of square miles, it is much more extensive than the country's limited land area. No wonder the Marshalls' coral reef is one of the most utilized resources by the people of the country!

On the other extreme, the Marshall Islands are home to one of the "poorest" (in terms of species diversity) natural ecosystems left on earth. Bokak Atoll, the most northerly atoll in the Republic of the Marshall Islands, has only 9 species of land plants. However, 26 species of birds have been reported there at one time or another, 12 breeding. A species of wide-ranging skink, the not-so-harmful Polynesian rat and land hermit crabs, along with some insects and other arthropods, just about complete its land fauna. Its total land area is only 1 1/4 square miles.

But therein lies Bokak's uniqueness. It is considered to be one of the last remaining untouched arid atolls on earth, and hence considered worthy of consideration as protection as a complete preserve, with human visitation highly restricted.

The contrast between these two ecosystems is striking, and not just because one is marine and the other terrestrial. The bigger difference is in the number of species of plants and animals comprising each ecosystem.

According to the well-known botanist Dr. F. R. Fosberg, who did extensive studies of the Marshall Islands for many years: "an ecosystem is a habitat of any magnitude, simple or complex, with all the plants and animals included in it." He further stated that by such a definition, an ecosystem can be anything "from a droplet of water with a bacterium in it to the earth itself, with all the plants and animals in it, or, conceivably, the universe with all its inhabitants - if there are any beyond earth's confines."

More massive ecosystems are often subdivided. These have a variety of names, such as communities, forests, woodlands, reef flats, habitats, communities, and others. But they all fall within the definition of the Convention on Biological Diversity of ecosystem, "a dynamic complex of plant, animal and microorganism communities and their non-living environments interacting as a functional unit."

The size of these subunits is more a case of convenience than biology. Within the gigantic superecosystem of the coral reef of the Marshall Islands, there are the ocean reef ecosystem and the lagoon reef ecosystem. Within the ocean reef ecosystem, there are the calm water ecosystems, which differs from the wave-swept ecosystems. In the moderately strong wave swept ocean reef ecosystem, there is the micro-ecosystem of the Pocillopora coral community, with an assortment of animal species unique to the branching species of P. eydouxi, P. meandrina and P. elegans. Some of the fishes and crustaceans can only be found in those corals.

On the high seas, there is an ecosystem associated with the Portuguese man-of-war (Physalia utricia). Certain fishes are immune to this animal's stinging tentacles, but it is conversely preyed upon by floating mollusks and other marine animals.

Similarly, on land, a single tree can be its own ecosystem. The seaside "utilomar" (Guenarda speciosa) is pollinated by a sphynx moth (Cephonodes picus), but as if part of the price for the insect's beneficial services, that same moth's caterpillars feed on the tree's leaves. Spiders set up their webs between the smaller branches, and birds light on the larger ones, where lichens grow. Down below, fallen leaves and the droppings from the birds and caterpillars form a mat of humus, where land hermit crabs and skinks scamper about.

Yet ecosystems, large or small, are not separate entities. As marine scientist Alan White explained that ecosystems "although labeled separately, are mutually interdependent." As he further pointed out, "living organisms, mineral and organic matter, and energy move through the boundaries on a regular basis." Moreover, under extreme or extraordinary circumstances, ecosystems may depart from their standard "neat packages." For example, after Typhoon Axel hit Majuro in 1991, numerous yellowfin scorpionfishes (Sebastapistes cyanostigma), that are supposed to "live exclusively among the branches of robust Pocillipora corals" were observed resting on branched species of Acropora, even looking somewhat forlorn, likely because their former homes had been destroyed by the powerful storm waves.

As interesting as each and every ecosystem is, for the sake of this report, the focus is mainly on the traditionally recognized ones. Nevertheless, none of these ecosystems will be identical in any two locations. Furthermore, since humans have had such a strong impact on the biota of the Marshalls, it is not practical, or even really possible, to separate "natural" ecosystems from "artificial" ones, athough extreme examples of both should be self-evident. And in the Marshall Islands, it is not even possible to have a sharp demarcation between terrestrial and marine ecosystems.